Conventional phase-changeable random access memories (PRAMs) may utilize a metal-oxide semiconductor (MOS) field effect transistor to control switching within a PRAM cell having a phase-changeable memory element therein. A phase-changeable memory element may utilize a phase-changeable material such as germanium-antimony-tellurium (GST), which is susceptible to phase changes in response to Joule heating. These phase changes enable the material to operate as a non-volatile storage medium for binary data. However, the use of a MOS field effect transistor within each PRAM cell may result in an unnecessarily large layout footprint for each cell and thereby reduce integration density of large PRAM arrays. The use of a MOS field effect transistor may also increase fabrication costs.
One example of a non-volatile phase changeable storage device is illustrated in U.S. Pat. No. 6,750,469 to Ichihara et al. Another non-volatile storage device is illustrated in U.S. Patent Publication No. 2003/0193053 to Gilton. This storage device may include a diode and a memory cell having chalcogenide glass therein. This chalcogenide glass may be formed as a germanium selenide layer.